Issue #2969807 by jmikii: Fix "LinkField is deprecated in Drupal 8.3.x and...

Issue #2969807 by jmikii: Fix "LinkField is deprecated in Drupal 8.3.x and will be be removed before Drupal 9.0.x. Use \Drupal\link\Plugin\migrate\field\d7\LinkField instead." deprecation message